Exploring Classes and Objects in Java: Understanding the Fundamentals

Updated on September 18, 2024

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7 min read

ARTICLE OUTLINE

Introduction to Classes and Objects in Java What is a Class in Java?What is an Object in Java?How to Create an Object of a Class Difference Between Java Class and Object Conclusion FAQs

In this article, you will find out the fundamental idea of classes and objects in Java. With classes and objects in Java, object-oriented programming techniques allow us to create new programs. Java classes are solely intellectual entities, but objects in Java can be both logical and physical. This article aims to aid new programmers in achieving their desire to be adept at using Java-based building blocks.

Introduction to Classes and Objects in Java

Classes and objects in Java, including their functionalities and characteristics, are the core foundation of all that you know about Java. For instance, an automobile is an object in the actual world. The car contains characteristics like weight and color, as well as functions like acceleration and brake. A class functions as a kind of object constructor or “blueprint” for making new things. Let’s explore Java objects in a bit more detail, starting with the class.

What are Classes and Objects?

Classes and objects in Java are the two most crucial Java concepts and notions any developer has to know and understand. Classes and objects in Java have a close relationship and collaborate. An object is a class instance and has states (variables) and behaviors. A cat is an example of an object; its size and color are variables, while its actions, such as purring and scratching stuff, are behaviors. A class serves as a blueprint or template for the object, outlining the state or behavior that objects of that type can support.

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What is a Class in Java?

In Java, a class represents an idea, which preserves a collection of characteristics that capture the context-dependent meaning-making. For instance, a class may be used to represent a car together with all of its parts and connected operations. ModelName, regNumber, and owner are characteristics of our automobile model, and startEngine(), accelerate(), and stop() are methods.

Characteristics of Class in Java

It’s crucial to understand the characteristics of classes and objects in Java to become proficient in this oriented-programming language. Here are the characteristics of a class in Java:

A class serves as an object creation template.
It describes an object’s state and behavior.
Objects are initialized using constructors.
Classes may inherit characteristics from other classes.

Declare Class in Java

<preid=”Object”>access_modifier class { // Super() keyword refers to parent class return super.clone(); } String name = “HeroVired”; // Method 2 // main driver method public static void main(String[] args) { GFG obj1 = new GFG(); // Try block to check for exceptions try { GFG obj2 = (GFG)obj1.clone(); System.out.println(obj2.name); } catch (CloneNotSupportedException e) { e.printStackTrace(); } } } Output: Hero Vired Let’s explore Java objects in a bit more detail.

What is an Object in Java?

Objects serve as a representation of a real-world thing. When modeling an entity, you must decide on its state and the range of possible actions. This thinking method is considered the foundation of object-oriented programming. In Java, it’s crucial to distinguish between an Object and an instantiated object. The base class of all Java objects that are instantiated is called an Object.

Characteristics of Object in Java

Check the characteristics of an object in Java to compare better the characteristics of both classes and objects in Java:

- Classes have instances that are objects.

- The state and the behavior of objects.

- Things are capable of speaking to one another.

- The ability to inherit from other objects exists.

Declare Object in Java

A class is deemed to be instantiated whenever an object belonging to it is produced. The class’s characteristics and behavior are shared in all instances. However, the states of those characteristics, or their values, are particular to each object. Any number of instances may exist for a single class.

Object and Class Example: Initialization Through Reference

Here are some of the key ways to define Defining Classes and Creating Objects in Java.

class Student{  
 int id;  
 String name;  
}  
class TestStudent2{  
 public static void main(String args[]){  
  Student s1=new Student();  
  s1.id=250;  
  s1.name="Rahul";  
  System.out.println(s1.id+" "+s1.name);//printing members with a white space  
 }  
}  

Output:
250 Rahul

Object and Class Example: Initialization Through Method

Here is an example of java Object and Class initializing through methods

class Student{  
 int rollno;  
 String name;  
 void insertRecord(int r, String n){  
  rollno=r;  
  name=n;  
 }  
 void displayInformation(){System.out.println(rollno+" "+name);}  
}  
class TestStudent4{  
 public static void main(String args[]){  
  Student s1=new Student();  
  Student s2=new Student();  
  s1.insertRecord(321,"Mayank");  
  s2.insertRecord(425,"Sonali");  
  s1.displayInformation();  
  s2.displayInformation();  
 }  
}  

Output:
321 Mayank
425 Sonali

Object and Class Example: Main Within the Class

Here is an example of java Object and Class within the class

class Lamp {
  
  // stores the value for switch
  // true if switch is on
  // false if switch is off
  boolean isOn;

  // method to turn on the switch
  void turnOn() {
    isOn = true;
    System.out.println("Switch on? " + isOn);

  }

  public static void main(String[] args) {
    
    // create an object of Lamp
    Lamp led = new Lamp();

    // access method using object
    led.turnOn();
  }
}

Output:
Switch on? true

Object and Class Example: Main Outside the Class

Here is an example of java Object and Class outside the class

class Lamp {
  
  // stores the value for switch
  // true if switch is on
  // false if switch is off
  boolean isOn;

  // method to turn on the switch
  void turnOn() {
    isOn = true;
    System.out.println("Switch on? " + isOn);

  }

  // method to turnoff the switch
  void turnOff() {
    isOn = false;
    System.out.println("Switch on? " + isOn);
  }
}

class Main {
  public static void main(String[] args) {

    // create objects led and halogen
    Lamp led = new Lamp();
    Lamp halogen = new Lamp();

    // turn on the switch by
    // calling method turnOn()
    led.turnOn();

    // turn off the switch by
    // calling method turnOff()
    halogen.turnOff();
  }
}

Output:
Switch on? true
Switch on? False

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How to Create an Object of a Class

The following are the three straightforward stages of creating a Java object:

Declaration: The initial step in creating an object is called a declaration. You must declare a variable in this step with the class name as the data type.
Instantiation: The following step is instantiation, where you must build the object using the ‘new’ keyword.
Initialization: To complete the third step, you must execute the class constructor to begin initializing the object.

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Difference Between Java Class and Object

Here is a list of major difference between java Class and Objects in detail to make to you understand better.

Java Class	Java Objects
A class’s declaration does not allow any memory.	When an object is formed, memory is allocated immediately.
A logical entity is a class.	An object is a tangible class.
You can only declare a class once.	The number of times an object can be produced depends on the need.
The blueprint for an object is its class. It is utilized for making objects.	An instance of the class exists in an object.
An automobile is a good illustration of class.	The class automobile can contain items like a BMW, Ferrari, etc.

Conclusion

We hope that this article has improved your comprehension of the fundamental ideas pertaining to Java objects and classes, the procedures needed to declare them, and their primary distinctions. Are you eager to learn more about Java and acquire a certification? Then look into HeroVired’s Full Stack Development course, which the most knowledgeable current market professionals put together.

FAQs

What are access modifiers, and how do they control the visibility of class members?

The visibility of a class's properties, methods, and constructors can be managed with the access modifiers keyword. Private, default, protected, and public are the four access modifiers recognized by Java.

How do you override methods in Java, and what is the significance of polymorphism?

Method Overriding is a technique for achieving Runtime polymorphism. When a child or subclass has a technique with the identical name, variables, and return type as the parent class or the superclass, that technique overrides the function in the superclass. This is known as method overriding. Learn more about polymorphism in Java to better understand classes and objects in Java.

What is the function of the "this" keyword in Java? Also, how is it used within a class?

In a method or constructor, the ‘this’ keyword refers to the current object. As a class attribute is shadowed by a method or constructor argument, the ‘this’ keyword is used to clarify and mitigate the differences between class attributes and parameters with the same name.

Is garbage collection fully-functional in Java? And how does it manage memory for objects?

The heap is where Java objects are kept. The heap is formed when the JVM starts up, and its size might change as an application is running. Garbage is collected once the pile is full.

Updated on September 18, 2024

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